BALTIMORE (AP) — The best 3-year-old in the land just happens to be a filly named Rachel Alexandra.

Jockey Calvin Borel all but guaranteed victory in the Preakness Stakes and, boy, did his horse deliver, becoming the first filly in 85 years to win the second leg of the Triple Crown.

A rangy bay who is as big as most of the horses she beat, Rachel Alexandra shot to the front and took a sizable lead before Mine That Bird tested her in the stretch. The 9-5 favorite beat him by a length in her first race against the boys.

Saturday’s win also validated Borel’s decision to climb off Kentucky Derby winner Mine That Bird and stay on as her regular rider.

Now Borel may get a shot at a personal Triple Crown, if Rachel Alexandra goes on to the Belmont Stakes in three weeks. The 1 1/2-mile race is the most grueling of the three.

‘‘I’m not worried about nothing,’’ he said. ‘‘It’s going to take a racehorse to beat her.’’

Rachel Alexandra had already beaten up on her own gender, winning her five previous races by a combined 43 1/2 lengths.

Musket Man finished third, as he did in the Derby, followed by Flying Private and Big Drama.

Rachel Alexandra covered 1 3-16 miles in 1:55.08 and became the first horse to win at Pimlico from the No. 13 post on the far outside. She paid $5.60, $4.60 and $3.60. Mine That Bird returned $6.60 and $4.80, while Musket Man paid $5 to show.

The winner earned $660,000 from the purse of $1.1 million.

Papa Clem was sixth, followed by Terrain, Luv Gov, General Quarters, Friesan Fire, Pioneerof the Nile, Tone It Down and Take the Points.

The last filly to win the Preakness was Nellie Morse in 1924. Rachel Alexandra became the second filly to go off as the wagering favorite and win. Whimsical at 8-5 odds was the first, in 1906.

The ending was far different from the last time a filly challenged the boys. Eight Belles finished a gallant second in last year’s Kentucky Derby, then broke both front legs while galloping past the finish line and was destroyed on the track.

This time, it was all cheers. No tears.

Rachel Alexandra, marked by two white spots on her head, wasn’t even supposed to be in the Preakness. Her original owners, who named the filly after a 13-year-old granddaughter, didn’t nominate her to the Triple Crown races, believing fillies should run only against their own gender.

After her stunning victory by 20 1/4 lengths in the Kentucky Oaks, the day before the Derby, Rachel Alexandra was sold to Jess Jackson, founder of Kendall-Jackson winery, and Harold McCormick.

They ponied up $100,000 to buy her a spot in the race, and the gamble paid off.

‘‘There was a lot of social criticism and doubt about whether she was capable,’’ Jackson said. ‘‘I think I would’ve taken some heat if she hadn’t performed well, so that takes some heat off my shoulders.’’

Borel had total faith in the filly, making the unprecedented decision to dump Mine That Bird after his stunning Derby victory at 50-1 odds.

‘‘She’s the best horse in the country right now, bar none,’’ he said.